fix meta/salt with missing pillar

Change-Id: I4bc2f905a4218bc9c8d01e4a2de9fabc5af6b441
diff --git a/backupninja/meta/salt.yml b/backupninja/meta/salt.yml
index c60274b..89db0df 100644
--- a/backupninja/meta/salt.yml
+++ b/backupninja/meta/salt.yml
@@ -1,6 +1,6 @@
 grain:
   backupninja:
-    {%- if pillar.backupninja.client is defined %}
+    {%- if pillar.get('backupninja', {}).get('client') %}
     {%- from "backupninja/map.jinja" import service_grains with context %}
     {{ service_grains|yaml(False)|indent(4) }}
     {%- endif %}